Nymph (5)
(Other definitions for naiad that I've seen before include "Spring nymph" , "Aquatic larva of a dragonfly" , "Classic spirit" , "divine female figure" , "spirit in water" .)
'nymph' is the definition.
(dryad is a kind of nymph)
This is all the clue.
(Other definitions for dryad that I've seen before include "Nymph of the woods" , "Beautiful young woman" , "minor divinity" , "Wood-nymph" , "Woodland nymph" .)